JP7435617B2 - Negative electrode active material, negative electrode and secondary battery manufacturing method - Google Patents

Description

The present invention relates to a negative electrode active material, a negative electrode, and a secondary battery.

Conventionally, secondary batteries have been used as power sources for various electronic devices. A secondary battery generally has a structure in which an electrode assembly (electrode body) and an electrolyte are housed within an exterior body (case), and an external terminal (or electrode) for achieving electrical connection of the secondary battery. lead). The electrode assembly has a structure in which a positive electrode and a negative electrode are placed with a separator in between.

The positive electrode and the negative electrode each have a positive electrode layer containing a positive electrode active material and a negative electrode layer containing a negative electrode active material. In secondary batteries, ions are brought into the electrolyte due to the "positive electrode active material contained in the positive electrode layer" and the "negative electrode active material contained in the negative electrode layer," and these ions move between the positive electrode and the negative electrode. As a result, electrons are transferred and charged and discharged. In recent years, Li-ion secondary batteries using lithium ions have been widely used as power sources for electronic devices because they have excellent characteristics of high voltage and high energy density. In recent years, electronic devices have become smaller and more sophisticated, and there is a growing demand for higher energy density Li-ion secondary batteries.

The mainstream of current Li-ion secondary batteries is one using LiCoO ₂ for the positive electrode and graphite for the negative electrode. Although graphite for the negative electrode has excellent reversibility in charging and discharging, its discharge capacity has already reached a value close to the theoretical value of 372 mAh/g, which corresponds to the intercalation compound LiC ₆ . Therefore, in order to achieve even higher energy density, it is necessary to develop a negative electrode material with a higher discharge capacity than graphite. Therefore, as a negative electrode material to replace graphite, Si-based materials are attracting attention as an active material that forms an alloy with Li and has a discharge capacity that far exceeds that of graphite. Metal particles or alloy particles that absorb and release Li have a higher capacity density than graphite, which has been conventionally used as a negative electrode active material. Therefore, by using these as active materials, it is possible to increase the capacity of batteries, but these materials expand in volume when absorbing Li and contract when releasing Li, so particles Cracking of the film itself and cracking or peeling of the formed solid electrolyte interface film (hereinafter referred to as "SEI film") are likely to occur. The higher the capacitance density of the metal/alloy, the higher the expansion coefficient tends to be. When a high-capacity Si-based negative electrode material absorbs Li, its volume expands up to about four times, so cracking and destruction of the formed SEI film are particularly likely to proceed. For this reason, the reductive decomposition of the electrolyte increases during charging, making it impossible to obtain cycle characteristics at a practical level.

Therefore, techniques have been disclosed in which decomposition of the electrolytic solution can be suppressed by coating a Si-based negative electrode material or the like with a specific metal oxide or metal (for example, Patent Documents 1 to 4).

Japanese Patent Application Publication No. 2008-4534 Special table 2016-507859 publication WO2017/126337 Japanese Patent Application Publication No. 2004-335334

The inventors of the present invention discovered that the following problems occur. Specifically, as shown in FIG. 3, the conventional negative electrode active material 100 has a negative electrode active material core 101 and a coating 102 formed on the surface of the negative electrode active material core, and expands and contracts during charging and discharging. Repeated. At this time, since the conventional coating 102 does not have sufficient followability (or restorability) against expansion and contraction, as shown in FIG. Physical deterioration such as peeling 1022 from 101 easily occurred. As a result, a new negative electrode material surface was generated, which promoted the decomposition of the electrolytic solution, resulting in a rapid deterioration of cycle characteristics. In addition, as the electrolyte decomposes, cracks in various parts of the particles are promoted, and side reactions of the electrolyte increase, resulting in side reaction products that further increase the particle volume and further deteriorate charge/discharge efficiency. . FIG. 3 is a schematic cross-sectional view of a negative electrode active material for explaining expansion and contraction in a conventional negative electrode active material. FIG. 4 is a schematic cross-sectional view showing the surface state of a conventional negative electrode active material.

An object of the present invention is to provide a battery negative electrode active material that exhibits sufficiently excellent initial charge/discharge efficiency and cycle characteristics by suppressing physical deterioration of the coating due to expansion and contraction of the core material.

The present invention
A negative electrode active material for a battery, comprising: a negative electrode active material core; and a coating formed on the surface of the negative electrode active material core,
The coating is
An organic-inorganic hybrid consisting of a reactant containing at least a first metal alkoxide containing no metal atom-carbon atom bond in one molecule; and a second metal alkoxide containing two or more metal atom-carbon atom bonds in one molecule. The present invention relates to a negative electrode active material that is a film.

The negative electrode active material of the present invention suppresses physical deterioration of the coating due to expansion and contraction of the core material (e.g., cracks, pinholes, and peeling from the negative electrode active material core material), thereby achieving sufficiently excellent initial charge and discharge. Efficiency and cycle characteristics can be shown.

FIG. 2 is a schematic cross-sectional view of a negative electrode active material for explaining expansion and contraction in the negative electrode active material of the present invention. FIG. 2 is a schematic cross-sectional view showing the surface state of the negative electrode active material of the present invention. FIG. 2 is a schematic cross-sectional view of a negative electrode active material for explaining expansion and contraction in a conventional negative electrode active material. FIG. 2 is a schematic cross-sectional view showing the surface state of a conventional negative electrode active material.

[Negative electrode active material]
As shown in FIG. 1, the negative electrode active material 10 of the present invention has a negative electrode active material core material 1 and a coating 2 formed on the surface of the negative electrode active material core material 1, and repeatedly expands and contracts due to charging and discharging. You may be FIG. 1 is a schematic cross-sectional view of a negative electrode active material for explaining expansion and contraction in the negative electrode active material of the present invention.

The negative electrode active material core material 1 is a material that contributes to the intercalation and desorption of ions that move between the positive electrode and the negative electrode and is responsible for the transfer of electrons, and from the viewpoint of increasing battery capacity, it is a material that contributes to the intercalation and desorption of lithium ions. It is preferable that there be. From this point of view, it is preferable that the negative electrode active material core material is, for example, various silicon-based materials, carbon-based materials, or a mixture thereof. From the viewpoint of further increasing battery capacity, the negative electrode active material core is preferably a silicon-based material.

A silicon-based material is a general term for materials containing silicon (Si) as a constituent element. The silicon-based material may be simple silicon, a silicon alloy, or a silicon compound. Further, the silicon-based material may be a material having at least a portion of any one or two or more types of phases among the above-mentioned simple substance, alloy, and compound. Note that the silicon-based material may be crystalline or amorphous. Silicon is classified as a metal.

Silicon is a simple substance in a general sense. That is, the purity of a simple substance does not necessarily need to be 100%, and the simple substance may contain a trace amount of impurity.

The silicon alloy may contain two or more kinds of metal elements as constituent elements, or may contain one or more kinds of metal elements and one or more kinds of metalloid elements as constituent elements. Further, the silicon alloy described above may further contain one or more nonmetallic elements as a constituent element. The structure of a silicon alloy is, for example, a solid solution, a eutectic (eutectic mixture), an intermetallic compound, or a coexistence of two or more thereof. The metal elements and metalloid elements contained as constituent elements in the silicon alloy are, for example, one or more of metal elements and metalloid elements that can form an alloy with the electrode reactant. be. Specific examples include magnesium, boron, aluminum, gallium, indium, germanium, tin, lead, bismuth, cadmium, silver, zinc, hafnium, zirconium, yttrium, palladium, and platinum. For example, the silicon alloy may contain any one of tin, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony, and chromium as a constituent element other than silicon. Contains two or more types.

The silicon compound contains, for example, one or more of carbon and oxygen as constituent elements other than silicon. Note that the silicon compound may contain, for example, as a constituent element other than silicon, one or more of the series of elements described for the silicon alloy.

Silicon alloys and silicon compounds include, for example, _SiB4 , _SiB6 , _Mg2Si , _Ni2Si , _TiSi2 , _MoSi2 , _CoSi2 , _NiSi2 , _CaSi2 , _CrSi2 , _Cu5Si , _FeSi2, MnSi ₂ , NbSi ₂ , TaSi ₂ , VSi ₂ , WSi ₂ , ZnSi ₂ , SiC, Si ₃ N ₄ , Si ₂ N ₂ O, SiO _v (0<v≦2), SiTi _w (0<w≦2) , and LiSiO. Note that v in SiO _v may be 0.2<v<1.4. In SiTi _w , w may be 0.01≦v≦0.5.

Carbon-based materials are a general term for materials containing carbon as a constituent element. The type of carbon-based material is not particularly limited, but includes, for example, graphitizable carbon, non-graphitizable carbon, and graphite (natural graphite, artificial graphite). However, it is preferable that the spacing between the (002) planes related to non-graphitizable carbon is, for example, 0.37 nm or more, and the spacing between the (002) planes related to graphite is, for example, 0.34 nm or less. is preferred. More specifically, carbon-based materials include, for example, pyrolytic carbons, cokes, glassy carbon fibers, fired organic polymer compounds, activated carbon, and carbon blacks. The cokes include, for example, pitch coke, needle coke, petroleum coke, and the like. The fired organic polymer compound is a fired (carbonized) product of a polymer compound, and the polymer compound is, for example, one or more of phenol resins, furan resins, and the like. In addition, the carbon-based material may be, for example, low-crystalline carbon heat-treated at a temperature of about 1000° C. or less, or amorphous carbon. The carbon-based material may be hard carbon, soft carbon, or diamond-like carbon.

The shape of the carbon-based material is not particularly limited, and examples thereof include fibrous, spherical (particulate), and scaly shapes. Of course, carbon-based materials having two or more types of shapes may be mixed.

The negative electrode active material core material may be a metal oxide containing a metal other than silicon. Examples of such metal oxides include at least one selected from the group consisting of tin oxide, indium oxide, zinc oxide, lithium oxide, and the like.

The average particle diameter of the negative electrode active material core material is not particularly limited, and may be, for example, 1 μm or more and 50 μm or less, particularly 1 μm or more and 40 μm or less. The average particle diameter described here is the median diameter D50 (μm), and the same applies hereafter.
When the negative electrode active material core material is a silicon-based material, the average particle size (median diameter D50) is preferably 1 μm or more and 10 μm or less from the viewpoint of suppressing side reactions and expansion of the electrolytic solution.
When the negative electrode active material core material is a carbon-based material, the average particle size (median diameter D50) is preferably 5 μm or more and 40 μm or less from the viewpoint of suppressing side reactions and expansion of the electrolytic solution.

The coating 2 is an organic-inorganic hybrid coating, and is formed from a composite of an organic component and an inorganic component. Specifically, the coating 2 is formed from a reactant containing at least a first metal alkoxide and a second metal alkoxide as monomer components. More specifically, the coating 2 is not a stack of multiple layers formed from each of the metal alkoxides, but has a network structure (single layer structure) made of reactants of the metal alkoxides. . Since the coating 2 is composed of a reactant containing at least a first metal alkoxide and a second metal alkoxide, it has high flexibility (restorability) and high resistance to expansion and contraction of the core material. Specifically, even if the negative electrode active material core repeatedly expands and contracts due to charging and discharging, the coating 2 can sufficiently follow such expansion and contraction. Therefore, it is considered that physical deterioration of the coating 2 due to expansion and contraction of the core material 1 can be sufficiently suppressed, and sufficiently excellent initial charge/discharge efficiency and cycle characteristics can be obtained. Although the details of the mechanism by which such an effect is obtained in the present invention are not clear, it is thought to be based on the following mechanism. Specifically, the coating 2 is composed of a reactant containing at least a first metal alkoxide and a second metal alkoxide, so as shown in FIG. 1, the coating 2 includes an inorganic portion 2a and an organic portion 2b. The inorganic part 2a is a part based on both the first metal alkoxide and the second metal alkoxide, and the organic part 2b is a part based on a part of the second metal alkoxide. Since the organic part 2b has higher flexibility than the inorganic part 2a, even if the core material 1 expands (see the right side in FIG. 1) or contracts (see the left side in FIG. 1), the core material By following the expansion and contraction, as shown in FIG. 2, physical deterioration of the coating 2 can be sufficiently suppressed. The coating 2 can be designed as an inorganic material that has the characteristics (flexibility) of an organic material by hybridizing an organic material and an inorganic material. For example, organic materials such as plastics are light, have excellent processability, and have flexibility and impact resistance. On the other hand, organic materials are inferior to inorganic materials in heat resistance and material stability. On the other hand, although inorganic materials such as silica and glass have excellent durability and heat resistance, they are often heavy and weak against impact (brittle, low flexibility). In the present invention, since the film 2 is an organic-inorganic hybrid material, it is possible to incorporate the characteristics of both of them. If the coating does not contain a second metal alkoxide, the coating cannot sufficiently follow the expansion and contraction of the core material, so physical deterioration of the coating is not sufficiently suppressed, resulting in sufficiently excellent initial charge/discharge efficiency. and cycle characteristics cannot be obtained. FIG. 2 is a schematic cross-sectional view showing the surface state of the negative electrode active material of the present invention.

The coating 2 usually has an average thickness of, for example, 0.1 nm or more and 20 nm or less (particularly 0.5 nm or more and 15 nm or less).

The first metal alkoxide is a metal alkoxide that does not contain any metal atom-carbon atom bond in one molecule, and is a metal alkoxide in which all hands of the metal are bonded to an alkoxy group (-OR ¹ ). In the first metal alkoxide, the metal atom-carbon atom bond is a direct covalent bond between a metal atom and a carbon atom. In the first metal alkoxide, the carbon atoms constituting the metal atom-carbon atom bond are carbon atoms constituting monovalent hydrocarbon groups (for example, alkyl groups and alkenyl groups) or divalent hydrocarbon groups (for example, alkylene groups). carbon atoms that make up the group). The first metal alkoxide does not have any such metal atom-carbon atom bond in one molecule. Therefore, the first metal alkoxide forms the coating 2 and fixes the coating 2 to the negative electrode active material core 1 through a relatively strong bond.

Specifically, the first metal alkoxide is a compound represented by the following general formula (1).

In formula (1), ^M1 is a metal atom, and is Si, Ti, Al, or Zr, and is preferably Si, Ti, or Zr from the viewpoint of further improving the initial charge/discharge efficiency and cycle characteristics of the negative electrode active material. It is Al, more preferably Si or Ti, and still more preferably Si.
x is the valence of ^M1 . When M ¹ is Si, Ti or Zr, x is 4. When ^M1 is Al, x is 3.
R ¹ is each independently an alkyl group having 1 to 10 carbon atoms or a group represented by the general formula: -C(R ² )=CH-CO-R ³ (wherein R ² and R ³ are , as described below), and is preferably an alkyl group having 1 to 5 carbon atoms from the viewpoint of further improving the initial charge/discharge efficiency and cycle characteristics of the negative electrode active material. Examples of the alkyl group as R ¹ include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, n-pentyl group, n-hexyl group. group, n-heptyl group, n-octyl group, n-nonyl group, n-decyl group, etc. For a plurality of R ^1s depending on the number of x, all R ^1s may be each independently selected from the above alkyl groups, or all R ^1s may be mutually selected from the above alkyl groups. They may be the same group.
R ² is an alkyl group having 1 to 10 carbon atoms, and is preferably an alkyl group having 1 to 5 carbon atoms from the viewpoint of further improving the initial charge/discharge efficiency and cycle characteristics of the negative electrode active material. Examples of the alkyl group as ^R2 include the same alkyl groups as the alkyl group as ^R1 .
R ³ is an alkyl group having 1 to 30 carbon atoms, an alkyloxy group having 1 to 30 carbon atoms, or an alkenyloxy group having 1 to 30 carbon atoms, which improves the initial charge/discharge efficiency and cycle characteristics of the negative electrode active material. From the viewpoint of improvement, preferably an alkyl group having 1 to 20 carbon atoms (more preferably 1 to 10, even more preferably 1 to 5), an alkyloxy group having 10 to 30 carbon atoms (especially 14 to 24), or It is an alkenyloxy group having 10 to 30 (especially 14 to 24) carbon atoms. Preferred alkyl groups for ^R3 include the same alkyl groups as the alkyl group for ^R1 , as well as undecyl, lauryl, tridecyl, myristyl, pentadecyl, cetyl, heptadecyl, stearyl, nonadecyl groups, Examples include eicosyl group. Examples of the alkyloxy group as R ³ include a group represented by the formula: -OC _p H _2p+1 (wherein p is an integer of 1 to 30). Examples of the alkenyloxy group as R ³ include a group represented by the formula: -O-C _q H _2q-1 (wherein q is an integer from 1 to 30).

In formula (1), when two adjacent R ^1s among the plurality of R ¹ are alkyl groups, they are bonded to each other to form an oxygen atom to which the two R ^1s are bonded and an M ¹ to which the oxygen atom is bonded. Together with the atoms, a ring (for example a 5- to 8-membered ring, especially a 6-membered ring) may be formed. An example of a ring formed by bonding two adjacent R ¹ to each other is a 6-membered ring represented by the general formula (1X).

In formula (1X), R ⁴ , R ⁵ and R ⁶ are each independently a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and further improve the initial charge/discharge efficiency and cycle characteristics of the negative electrode active material. From this viewpoint, a hydrogen atom or an alkyl group having 1 to 5 carbon atoms is preferred. The total number of carbon atoms of R ⁴ , R ⁵ and R ⁶ is usually 0 to 12, and preferably 2 to 8 from the viewpoint of further improving the initial charge/discharge efficiency and cycle characteristics of the negative electrode active material. In formula (1X), examples of the alkyl groups for R ⁴ , R ⁵ and R ⁶ include the same alkyl groups as the alkyl group for R ¹ .

Examples of the first metal alkoxide include compounds represented by the following general formulas (1A), (1B), (1B'), (1C) and (1D). The first metal alkoxide is a compound represented by the general formula (1A), (1B), (1C) or (1D) or a mixture thereof, from the viewpoint of further improving the initial charge/discharge efficiency and cycle characteristics of the negative electrode active material. It is preferably a compound represented by general formula (1A), (1B) or (1C) or a mixture thereof, and a compound represented by general formula (1A) or (1B) or them It is more preferable that it is a mixture of the following, and it is particularly preferable that it is a compound represented by the general formula (1A) or a mixture thereof.

In formula (1A), R ¹ is each independently the same R ¹ as R ¹ in formula (1). R ¹ is each independently an alkyl group having preferably 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms, from the viewpoint of further improving the initial charge/discharge efficiency and cycle characteristics of the negative electrode active material.

Specific examples of the compound (1A) represented by such general formula are shown in the table below.

In formula (1B), R ¹ is each independently the same R ¹ as R ¹ in formula (1). From the viewpoint of further improving the initial charge/discharge efficiency and cycle characteristics of the negative electrode active material, R ¹ is preferably an alkyl group having 1 to 10 carbon atoms or the above general formula: -C(R ² ). A group represented by =CH-CO-R ³ (wherein R ² and R ³ are the same as R ² and R ³ , respectively, explained in general formula (1)), more preferably a carbon atom It is an alkyl group of number 1 to 10 (especially 1 to 5).
In formula (1B), each of R ² and R ³ is preferably the following group from the viewpoint of further improving the initial charge/discharge efficiency and cycle characteristics of the negative electrode active material. R ² is an alkyl group having 1 to 10 carbon atoms, preferably an alkyl group having 1 to 5 carbon atoms. Examples of the alkyl group as ^R2 include the same alkyl groups as the alkyl group as ^R1 . R ³ is an alkyl group having 1 to 30 carbon atoms, preferably an alkyl group having 1 to 20 carbon atoms (more preferably 1 to 10, still more preferably 1 to 5). Preferred alkyl groups for ^R3 include the same alkyl groups as the alkyl group for ^R1 , as well as undecyl, lauryl, tridecyl, myristyl, pentadecyl, cetyl, heptadecyl, stearyl, nonadecyl groups, Examples include eicosyl group.

Specific examples of the compound (1B) represented by such general formula are shown in the table below.

In formula (1B'), Ra ¹ , Ra ² , Ra ³ , Ra ⁴ , Ra ⁵ and Ra ⁶ are each independently a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and the negative electrode active material From the viewpoint of further improving initial charge/discharge efficiency and cycle characteristics, an alkyl group having 1 to 5 carbon atoms is preferable. The alkyl groups as Ra ¹ , Ra ² , Ra ³ , Ra ⁴ , Ra ⁵ and Ra ⁶ are the same as the alkyl group as R ¹ .

Specific examples of the compound (1B') represented by such general formula are shown in the table below.

In formula (1C), R ¹ is each independently the same R ¹ as R ¹ in formula (1). From the viewpoint of further improving the initial charge/discharge efficiency and cycle characteristics of the negative electrode active material, R ¹ is preferably an alkyl group having 1 to 10 carbon atoms or the above general formula: -C(R ² ). A group represented by =CH-CO-R ³ (wherein R ² and R ³ are the same as R ² and R ³ , respectively, explained in general formula (1)), more preferably a carbon atom It is an alkyl group of number 1 to 10 (especially 1 to 5).
In formula (1C), each of R ² and R ³ is preferably the following group from the viewpoint of further improving the initial charge/discharge efficiency and cycle characteristics of the negative electrode active material. R ² is an alkyl group having 1 to 10 carbon atoms, preferably an alkyl group having 1 to 5 carbon atoms. Examples of the alkyl group as ^R2 include the same alkyl groups as the alkyl group as ^R1 . R ³ is an alkyloxy group having 1 to 30 carbon atoms or an alkenyloxy group having 1 to 30 carbon atoms, preferably an alkyloxy group having 10 to 30 carbon atoms (particularly 14 to 24 carbon atoms), or an alkyloxy group having 1 to 30 carbon atoms; 10 to 30 (especially 14 to 24) alkenyloxy groups. Examples of the alkyloxy group as R ³ include a group represented by the formula: -OC _p H _2p+1 (wherein p is an integer of 1 to 30). Examples of the alkenyloxy group as R ³ include a group represented by the formula: -O-C _q H _2q-1 (wherein q is an integer from 1 to 30).

Specific examples of the compound (1C) represented by such general formula are shown in the table below.

In formula (1D), R ¹ is each independently the same R ¹ as R ¹ in formula (1). R ¹ is each independently an alkyl group having preferably 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms, from the viewpoint of further improving the initial charge/discharge efficiency and cycle characteristics of the negative electrode active material.

Specific examples of the compound (1D) represented by such general formula are shown in the table below.

Compound (1) represented by general formula (1) can be obtained as a commercially available product, or can be produced by a known method.
For example, compound (1A) can be obtained as a commercially available tetraethyl orthosilicate (manufactured by Tokyo Kasei Kogyo Co., Ltd.).
Further, for example, compound (1B) can be obtained as commercially available tetrabutyl orthotitanate (manufactured by Tokyo Kasei Kogyo Co., Ltd.) and T-50 (manufactured by Nippon Soda Co., Ltd.).
For example, compound (1B') can be obtained as a commercially available product, TOG (manufactured by Nippon Soda Co., Ltd.).
For example, compound (1C) can be obtained as a commercially available aluminum triisopropoxide (manufactured by Kanto Kagaku Co., Ltd.).
For example, compound (1D) can be obtained as commercially available zirconium (IV) tetrabutoxide under the trade names TBZR (manufactured by Nippon Soda Co., Ltd.) and ZR-181 (manufactured by Nippon Soda Co., Ltd.).

The content of the first metal alkoxide in the coating 2 (i.e., the reactant constituting the coating) is usually 10% by weight or more and 95% by weight based on the total amount (for example, the total amount of the first metal alkoxide and the second metal alkoxide). From the viewpoint of further improving the initial charge/discharge efficiency and cycle characteristics of the negative electrode active material, it is preferably 20% by weight or more and 80% by weight or less, and more preferably 25% by weight or more and 75% by weight or less. The coating may contain two or more types of first metal alkoxides, in which case the total amount thereof may be within the above range.

The second metal alkoxide is a metal alkoxide that contains two or more metal atom-carbon atom bonds in one molecule (e.g., 2 to 20, preferably 2 to 10, more preferably 2 to 5). In the second metal alkoxide, carbon atoms constituting two or more metal atom-carbon atom bonds are carbon atoms constituting monovalent hydrocarbon groups (e.g., alkyl groups and alkenyl groups) and/or divalent It is a carbon atom that constitutes a hydrocarbon group (for example, an alkylene group).In the second metal alkoxide, the carbon atoms that constitute all two or more metal atom-carbon atom bonds are From the viewpoint of further improving the cycle characteristics, carbon atoms constituting a divalent hydrocarbon group (for example, an alkylene group) are preferable.The metal atom of the second metal alkoxide is silicon. One molecule contains two or more metal atom-carbon atom bonds.For this reason, physical deterioration of the coating is suppressed.For example, in a second metal alkoxide, a metal atom-carbon atom bond is contained in the second metal alkoxide. When the constituent carbon atoms are carbon atoms constituting a divalent hydrocarbon group (e.g., an alkylene group), the presence of the divalent hydrocarbon group causes the coating to stretch when the core material expands. Follows the core material.For example, in a second metal alkoxide, when the carbon atoms forming the metal atom-carbon atom bond are carbon atoms forming a monovalent hydrocarbon group (for example, an alkyl group and an alkenyl group). When the core material contracts, the monovalent hydrocarbon group exerts a stress change relaxing effect (for example, a cushioning effect), and the coating follows the core material.As a result, physical deterioration of the coating 2 occurs. It is considered that this can sufficiently suppress the oxidation and provide sufficiently excellent initial charge/discharge efficiency and cycle characteristics.

When the carbon atoms constituting the metal atom-carbon atom bond in the second metal alkoxide are carbon atoms constituting a divalent hydrocarbon group, the second metal alkoxide has the following general formula (2) in one molecule. It is a compound having two or more trialkoxysilyl groups represented by

In formula (2), each R ²¹ is independently an alkyl group having 1 to 10 carbon atoms, and from the viewpoint of further improving the initial charge/discharge efficiency and cycle characteristics of the negative electrode active material, preferably the number of carbon atoms is It is an alkyl group having 1 to 5 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms. Examples of such alkyl groups include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, n-pentyl group, n-hexyl group, Examples include n-heptyl group, n-octyl group, n-nonyl group, n-decyl group and the like. Regarding the plurality of R ²¹ , all R ²¹ may be independently selected from the above alkyl groups, or all R ²¹ may be mutually the same group selected from the above alkyl groups. good.

The trialkoxysilyl groups possessed by the second metal alkoxide may be independently selected from the trialkoxysilyl groups represented by the above general formula (2), or may be the same group.

Specific examples of the trialkoxysilyl group represented by the general formula (2) are shown in the table below.

In the case where the carbon atoms constituting all two or more metal atom-carbon atom bonds in the second metal alkoxide are carbon atoms constituting a divalent hydrocarbon group, the second metal alkoxide is, for example, the following general It may be a compound represented by formula (2A), (2B), (2C), (2E) or (2F) or a mixture thereof. Among these, the second metal alkoxide is preferably a compound represented by general formula (2A), (2E) or (2F) or A mixture of these, more preferably a compound represented by general formula (2A).

In the case where the carbon atoms constituting all the two or more metal atom-carbon atom bonds in the second metal alkoxide are carbon atoms constituting a monovalent hydrocarbon group, the second metal alkoxide may be, for example, the following general It may be a compound represented by formula (2D) or a mixture thereof.

In formula (2A), R ²¹¹ and R ²¹² are each independently the same group as R ²¹ in formula (2). Specifically, three R ^211s and three R ²¹² are each independently an alkyl group having 1 to 10 carbon atoms, which is preferable from the viewpoint of further improving the initial charge/discharge efficiency and cycle characteristics of the negative electrode active material. is an alkyl group having 1 to 5 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms. The three R ^211s and the three R ²¹² may each be independently selected from R ²¹ in the above general formula (2), or may be the same group.
R ³¹ is a divalent hydrocarbon group having 1 to 20 carbon atoms, and is preferably a divalent hydrocarbon group having 1 to 10 carbon atoms from the viewpoint of further improving the initial charge/discharge efficiency and cycle characteristics of the negative electrode active material. It is a hydrocarbon group, more preferably a divalent hydrocarbon group having 1 to 8 carbon atoms, and even more preferably a divalent hydrocarbon group having 1 to 5 carbon atoms (especially 1 to 3). The divalent hydrocarbon group as R ³¹ may be a divalent saturated aliphatic hydrocarbon group (e.g. alkylene group) or a divalent unsaturated aliphatic hydrocarbon group (e.g. alkenylene group). Good too. The divalent hydrocarbon group as R ³¹ is preferably a divalent saturated aliphatic hydrocarbon group (particularly an alkylene group) from the viewpoint of further improving the initial charge/discharge efficiency and cycle characteristics of the negative electrode active material. The divalent saturated aliphatic hydrocarbon group (especially alkylene group) as R ³¹ is, for example, -(CH ₂ ) _p - (wherein p is 1 to 20, preferably 1 to 10, more preferably 1 to 8, more preferably an integer of 1 to 5 (particularly 1 to 3), and the like.

Specific examples of the compound (2A) represented by such general formula are shown in the table below.

In formula (2B), R ²¹¹ , R ²¹² , R ²¹³ and R ²¹⁴ are the same groups as R ²¹ in formula (2). Specifically, 3 R ²¹¹ , 3 R ²¹² , 3 R ²¹³ and 3 R ²¹⁴ are each independently an alkyl group having 1 to 10 carbon atoms, and the initial charge/discharge efficiency of the negative electrode active material and From the viewpoint of further improving cycle characteristics, an alkyl group having 1 to 5 carbon atoms is preferred, and an alkyl group having 1 to 3 carbon atoms is more preferred. Three R ²¹¹ , three R ²¹² , three R ²¹³ and three R ²¹⁴ may each be independently selected from R ²¹ in the above general formula (2), or may be the same group as each other. It's okay.
R ³² is each independently a divalent hydrocarbon group having 1 to 20 carbon atoms, and preferably has 1 to 20 carbon atoms from the viewpoint of further improving the initial charge/discharge efficiency and cycle characteristics of the negative electrode active material. A divalent hydrocarbon group having 10 carbon atoms, more preferably a divalent hydrocarbon group having 6 to 10 carbon atoms. The divalent hydrocarbon group as R ³² may be a divalent saturated aliphatic hydrocarbon group (e.g. alkylene group) or a divalent unsaturated aliphatic hydrocarbon group (e.g. alkenylene group). Good too. The divalent hydrocarbon group as R ³² is preferably a divalent saturated aliphatic hydrocarbon group (particularly an alkylene group) from the viewpoint of further improving the initial charge/discharge efficiency and cycle characteristics of the negative electrode active material. The divalent saturated aliphatic hydrocarbon group (especially alkylene group) as R ³² is, for example, -(CH ₂ ) _q - (wherein q is an integer of 1 to 10, more preferably 6 to 10). Examples include groups represented by: All R ³² 's may each be independently selected from the R ³² 's, or may be the same group as each other.
R ³³ is each independently a monovalent hydrocarbon group having 1 to 10 carbon atoms, and from the viewpoint of further improving the initial charge/discharge efficiency and cycle characteristics of the negative electrode active material, R 33 is preferably a monovalent hydrocarbon group having 1 to 10 carbon atoms. 5 monovalent hydrocarbon group, more preferably a monovalent hydrocarbon group having 1 to 3 carbon atoms. The monovalent hydrocarbon group as R ³³ may be a saturated aliphatic hydrocarbon group (eg, an alkyl group) or an unsaturated aliphatic hydrocarbon group (eg, an alkenyl group). The monovalent hydrocarbon group as R ³³ is preferably a saturated aliphatic hydrocarbon group (particularly an alkyl group) from the viewpoint of further improving the initial charge/discharge efficiency and cycle characteristics of the negative electrode active material. Examples of the monovalent saturated aliphatic hydrocarbon group (especially alkyl group) as R ³³ include methyl group, ethyl group, n-propyl, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert- Examples include butyl group, n-pentyl group, n-hexyl group, n-heptyl group, n-octyl group, n-nonyl group, n-decyl group and the like. All R ³³ 's may be independently selected from the R ³³ 's, or may be the same group as each other.

Specific examples of the compound (2B) represented by such general formula are shown in the table below.

In formula (2C), R ²¹¹ and R ²¹² are the same groups as R ²¹ in formula (2). Specifically, three R ²¹¹ and three R ²¹² are each independently an alkyl group having 1 to 10 carbon atoms, and from the viewpoint of further improving the initial charge/discharge efficiency and cycle characteristics of the negative electrode active material, Preferably it is an alkyl group having 1 to 5 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms. The three R ^211s and the three R ²¹² may each be independently selected from R ²¹ in the above general formula (2), or may be the same group.
R ³⁴ , R ³⁵ , and R ³⁶ are each independently a divalent hydrocarbon group having 1 to 10 carbon atoms, and from the viewpoint of further improving the initial charge/discharge efficiency and cycle characteristics of the negative electrode active material, Preferably it is a divalent hydrocarbon group having 1 to 5 carbon atoms. The divalent hydrocarbon groups as R ³⁴ , R ³⁵ , and R ³⁶ may be divalent saturated aliphatic hydrocarbon groups (for example, alkylene groups) or divalent unsaturated aliphatic hydrocarbon groups ( For example, it may be an alkenylene group). The divalent hydrocarbon groups as R ³⁴ , R ³⁵ , and R ³⁶ are preferably divalent saturated aliphatic hydrocarbon groups (especially alkylene basis). Examples of divalent saturated aliphatic hydrocarbon groups (especially alkylene groups) as R ³⁴ , R ³⁵ , and R ³⁶ include -(CH ₂ ) _r - (wherein r is 1 to 10, more preferably 1 (which is an integer of 5 to 5), and the like. All R ³⁴ , R ³⁵ , and R ³⁶ may each be independently selected from the above divalent hydrocarbon groups, or may be the same group. The total number of carbon atoms in R ³⁴ , R ³⁵ , and R ³⁶ is preferably 3 to 20, more preferably 6 to 10, from the viewpoint of further improving the initial charge/discharge efficiency and cycle characteristics of the negative electrode active material.

Specific examples of the compound (2C) represented by such general formula are shown in the table below.

In formula (2D), R ²¹¹ and R ²¹² are each independently the same group as R ²¹ in formula (2). Specifically, two R ²¹¹ and two R ²¹² are each independently an alkyl group having 1 to 10 carbon atoms, which is preferable from the viewpoint of further improving the initial charge/discharge efficiency and cycle characteristics of the negative electrode active material. is an alkyl group having 1 to 5 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms. Two R ²¹¹ and two R ²¹² may each be independently selected from R ²¹ in the above general formula (2), or may be the same group.

Specific examples of the compound (2D) represented by such general formula are shown in the table below.

In formula (2E), R ²¹² and R ²¹³ are the same groups as R ²¹ in formula (2). Specifically, three R ²¹² and three R ²¹³ are each independently an alkyl group having 1 to 10 carbon atoms, which is preferable from the viewpoint of further improving the initial charge/discharge efficiency and cycle characteristics of the negative electrode active material. is an alkyl group having 1 to 5 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms. The three R ^212s and the three R ^213s may each be independently selected from R ²¹ in the above general formula (2), or may be the same group.
R ³² is each independently a divalent hydrocarbon group having 1 to 20 carbon atoms, and preferably has 1 to 20 carbon atoms from the viewpoint of further improving the initial charge/discharge efficiency and cycle characteristics of the negative electrode active material. It is a divalent hydrocarbon group having 10 carbon atoms, more preferably a divalent hydrocarbon group having 4 to 8 carbon atoms. The divalent hydrocarbon group as R ³² may be a divalent saturated aliphatic hydrocarbon group (e.g. alkylene group) or a divalent unsaturated aliphatic hydrocarbon group (e.g. alkenylene group). Good too. The divalent hydrocarbon group as R ³² is preferably a divalent saturated aliphatic hydrocarbon group (particularly an alkylene group) from the viewpoint of further improving the initial charge/discharge efficiency and cycle characteristics of the negative electrode active material. The divalent saturated aliphatic hydrocarbon group (especially alkylene group) as R ³² is, for example, -(CH ₂ ) _q - (wherein q is 1 to 20, preferably 1 to 10, more preferably 4 to Examples include groups represented by (which is an integer of 8). All R ³² 's may each be independently selected from the R ³² 's, or may be the same group as each other.
R ³³ is each independently a monovalent hydrocarbon group having 1 to 10 carbon atoms, and from the viewpoint of further improving the initial charge/discharge efficiency and cycle characteristics of the negative electrode active material, R 33 is preferably a monovalent hydrocarbon group having 1 to 10 carbon atoms. 5 monovalent hydrocarbon group, more preferably a monovalent hydrocarbon group having 1 to 3 carbon atoms. The monovalent hydrocarbon group as R ³³ may be a saturated aliphatic hydrocarbon group (eg, an alkyl group) or an unsaturated aliphatic hydrocarbon group (eg, an alkenyl group). The monovalent hydrocarbon group as R ³³ is preferably a saturated aliphatic hydrocarbon group (particularly an alkyl group) from the viewpoint of further improving the initial charge/discharge efficiency and cycle characteristics of the negative electrode active material. Examples of the monovalent saturated aliphatic hydrocarbon group (especially alkyl group) as R ³³ include methyl group, ethyl group, n-propyl, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert- Examples include butyl group, n-pentyl group, n-hexyl group, n-heptyl group, n-octyl group, n-nonyl group, n-decyl group and the like. All R ³³ 's may be independently selected from the R ³³ 's, or may be the same group as each other.
R ³⁴ is each independently a monovalent hydrocarbon group having 1 to 30 carbon atoms, and preferably has 1 to 30 carbon atoms from the viewpoint of further improving the initial charge/discharge efficiency and cycle characteristics of the negative electrode active material. It is a monovalent hydrocarbon group having 10 carbon atoms, and more preferably a monovalent hydrocarbon group having 1 to 5 carbon atoms. The monovalent hydrocarbon group as R ³⁴ may be a saturated aliphatic hydrocarbon group (eg, an alkyl group) or an unsaturated aliphatic hydrocarbon group (eg, an alkenyl group). The monovalent hydrocarbon group as R ³⁴ is preferably a saturated aliphatic hydrocarbon group (especially an alkyl group) from the viewpoint of further improving the initial charge/discharge efficiency and cycle characteristics of the negative electrode active material. Examples of the monovalent saturated aliphatic hydrocarbon group (especially alkyl group) as R ³⁴ include methyl group, ethyl group, n-propyl, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert- Butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group, nonadecyl group, eicosyl group etc. All R ^34s may be independently selected from the R ^34s , or may be the same group as each other.

Specific examples of the compound (2E) represented by such general formula are shown in the table below.

In formula (2F), R ²¹² , R ²¹³ and R ²¹⁴ are each independently the same group as R ²¹ in formula (2). Specifically, three R ²¹² , three R ²¹³ and three R ²¹⁴ are each independently an alkyl group having 1 to 10 carbon atoms, and further improve the initial charge/discharge efficiency and cycle characteristics of the negative electrode active material. From this viewpoint, an alkyl group having 1 to 5 carbon atoms is preferred, and an alkyl group having 1 to 3 carbon atoms is more preferred. Three R ²¹² , three R ²¹³ and three R ²¹⁴ may each be independently selected from R ²¹ in the above general formula (2), or may be the same group.
R ³² is each independently a divalent hydrocarbon group having 1 to 20 carbon atoms, and preferably has 1 to 20 carbon atoms from the viewpoint of further improving the initial charge/discharge efficiency and cycle characteristics of the negative electrode active material. It is a divalent hydrocarbon group having 10 carbon atoms, and more preferably a divalent hydrocarbon group having 1 to 5 carbon atoms. The divalent hydrocarbon group as R ³² may be a divalent saturated aliphatic hydrocarbon group (e.g. alkylene group) or a divalent unsaturated aliphatic hydrocarbon group (e.g. alkenylene group). Good too. The divalent hydrocarbon group as R ³² is preferably a divalent saturated aliphatic hydrocarbon group (particularly an alkylene group) from the viewpoint of further improving the initial charge/discharge efficiency and cycle characteristics of the negative electrode active material. The divalent saturated aliphatic hydrocarbon group (especially alkylene group) as R ³² is, for example, -(CH ₂ ) _q - (wherein q is an integer of 1 to 10, more preferably 1 to 5). Examples include groups represented by: All R ³² 's may each be independently selected from the R ³² 's, or may be the same group as each other.

Specific examples of the compound (2F) represented by such general formula are shown in the table below.

Compound (2A) represented by general formula (2A), compound (2B) represented by general formula (2B), compound (2C) represented by general formula (2C), compound (2C) represented by general formula (2D), Compound (2D), compound (2E) represented by general formula (2E), and compound (2F) represented by general formula (2F) can be obtained as commercially available products, or can be obtained by known methods. It can also be manufactured.
For example, compound (2A) is commercially available as 1,2-bis(trimethoxysilyl)ethane (manufactured by Tokyo Kasei Kogyo Co., Ltd.) and 1,6-bis(trimethoxysilyl)hexane (manufactured by Tokyo Kasei Kogyo Co., Ltd.). can be obtained.
Further, for example, compound (2C) can be obtained as a commercial product, X-12-5263HP (manufactured by Shin-Etsu Chemical Co., Ltd.).
For example, compound (2D) can be obtained as a commercially available dimethyldimethoxysilane (manufactured by Tokyo Kasei Co., Ltd.).
Further, for example, compound (2F) can be obtained as a commercially available product, tris[3-(trimethoxysilyl)-propyl]isocyanurate (manufactured by Tokyo Kasei Co., Ltd.).

The second metal alkoxide may be, for example, a compound represented by general formula (2A), (2B), (2C), (2D), (2E) or (2F), or a mixture thereof. The second metal alkoxide is preferably a compound represented by the general formula (2A), (2D), (2E) or (2F) from the viewpoint of further improving the initial charge/discharge efficiency and cycle characteristics of the negative electrode active material, or A mixture of these, more preferably represented by the general formula (2A) (in particular, R ³¹ is a divalent hydrocarbon group having 1 to 5 carbon atoms (preferably 1 to 3); R ²¹¹ and R ²¹² are each represented by R ²¹¹ and R ²¹² in the above general formula (2A)) or (2D), or a mixture thereof.

The content of the second metal alkoxide in the coating 2 (that is, the reactant constituting the coating) is usually 5% by weight or more and 90% by weight based on the total amount (for example, the total amount of the first metal alkoxide and the second metal alkoxide). From the viewpoint of further improving the initial charge/discharge efficiency and cycle characteristics of the negative electrode active material, it is preferably 20% by weight or more and 80% by weight or less, and more preferably 25% by weight or more and 75% by weight or less. The coating may contain two or more types of second metal alkoxides, in which case the total amount thereof may be within the above range.

The content (i.e., coating amount) of the coating 2 in the negative electrode active material 10 is usually 0.20% by weight or more based on the total amount of the negative electrode active material 10 (i.e., the total amount of the negative electrode active material core material and the coating). % by weight or less, and from the viewpoint of further improving the initial charge/discharge efficiency and cycle characteristics of the negative electrode active material, preferably from 0.30% by weight to 3.20% by weight, more preferably from 0.30% by weight to 1. 000% by weight or less. In calculating the content, it was assumed that the entire amount of the alkoxide contained in the metal alkoxide undergoes a dehydration condensation reaction, and a reactant with no other changes in structure is obtained. For example, the weight of the reaction product obtained by dehydration condensation of all the alkoxides contained in 1 g of 1,2-bis(trimethoxysilyl)ethane is 0.49 g.

The negative electrode active material of the present invention can be produced by a method including stirring a negative electrode active material core material in an alkaline solvent together with a first metal alkoxide and a second metal alkoxide. After stirring, specifically, the negative electrode active material core material is filtered and washed, and then heated and dried to obtain a negative electrode active material in which a film is formed on the surface of the negative electrode active material core material. Note that the coating method is not limited to the above method as long as the active material core material can be coated, and coating methods such as spraying and dry mixing may be used.

The blending ratio (i.e. usage ratio) of the first metal alkoxide and the second metal alkoxide usually corresponds to the content ratio of each metal alkoxide in the coating, so the blending ratio can be adjusted according to the desired content ratio. .

The amount of the first metal alkoxide is usually 0.1 parts by weight or more and 20 parts by weight or less based on 100 parts by weight of the negative electrode active material core material, and is effective for further improving the initial charge/discharge efficiency and cycle characteristics of the negative electrode active material. From this point of view, the content is preferably 0.1 parts by weight or more and 10 parts by weight or less, more preferably 0.5 parts by weight or more and 2.0 parts by weight or less.

The amount of the second metal alkoxide is usually 0.1 parts by weight or more and 10 parts by weight or less based on 100 parts by weight of the negative electrode active material core material, and is effective for further improving the initial charge/discharge efficiency and cycle characteristics of the negative electrode active material. From this point of view, the content is preferably 0.1 parts by weight or more and 5 parts by weight or less, more preferably 0.2 parts by weight or more and 1.8 parts by weight or less.

The total amount of the first metal alkoxide and the second metal alkoxide is not particularly limited as long as a film is formed on the surface of the negative electrode active material core, and for example, 0.000 parts by weight per 100 parts by weight of the negative electrode active material core. The content is 5 parts by weight or more and 20 parts by weight or less, and from the viewpoint of further improving the initial charge/discharge efficiency and cycle characteristics of the negative electrode active material, preferably 0.5 parts by weight or more and 10 parts by weight or less, more preferably 0.8 parts by weight. The amount is 3.0 parts by weight or less. By adjusting the total blending amount, the content of the coating 2 (ie, the coating amount) in the negative electrode active material 10 described above can be controlled. The greater the total blending amount, the greater the coating amount.

The solvent is not particularly limited as long as it does not inhibit the reaction of the first metal alkoxide and the second metal alkoxide, and for example, monoalcohols, ethers, glycols, or glycol ethers are preferred. In a preferred embodiment, the solvent is methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, iso-butyl alcohol, 1-pentanol, 2-pentanol, 2-methyl-2-pentanol. Monoalcohols such as 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol, etc.; Glycols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol; dipropylene glycol monomethyl ether, diethylene glycol monomethyl ether , diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, or diethylene glycol monohexyl ether. Preferred solvents are monoalcohols. Moreover, water may be included if necessary. The above solvents may be used alone or in combination of two or more. The solvent may contain various additives such as catalysts, pH adjusters, stabilizers, thickeners, and the like. Examples of the additive include acid compounds such as boric acid compounds, and basic compounds such as ammonia compounds. The blending amount of the solvent is not particularly limited as long as each metal alkoxide can be uniformly present on the surface of the negative electrode active material core, and for example, 20 parts by weight or more and 200 parts by weight based on 100 parts by weight of the negative electrode active material core. In particular, the amount may be 30 parts by weight or more and 150 parts by weight or less.

The temperature of the mixture during stirring is not particularly limited as long as each metal alkoxide can be uniformly present on the surface of the negative electrode active material core material, and is, for example, 10°C or more and 70°C or less, preferably 15°C or more and 35°C or less. It is.
The stirring time is also not particularly limited as long as each metal alkoxide can be uniformly present on the surface of the negative electrode active material core material, and is, for example, 10 minutes or more and 5 hours or less, preferably 30 minutes or more and 3 hours or less.

Washing is performed to remove any remaining catalyst. For example, this can be done by contacting the residue from filtration with a washing solvent. The washing solvent is not particularly limited, and may be, for example, acetone.

The solvent used in washing is removed by heating and drying. The heating temperature is usually 15° C. or higher (particularly 15° C. or higher and 250° C. or lower), and preferably 15° C. or higher and 200° C. or lower from the viewpoint of solvent removal. The heating time is usually 30 minutes or more (particularly 30 minutes or more and 24 hours or less), and preferably 60 minutes or more and 12 hours or less from the viewpoint of solvent removal.

[Negative electrode]
The negative electrode of the present invention is composed of at least a negative electrode layer and a negative electrode current collector (foil), and the negative electrode layer contains the above-described coated negative electrode active material. The above-mentioned coated negative electrode active material of the negative electrode layer is composed of, for example, granules, and it is preferable that a binder is included in the negative electrode layer for sufficient contact between the particles and shape retention. Preferably, the negative electrode layer further contains a conductive additive to facilitate the transmission of electrons that promote battery reactions. Since the negative electrode layer contains a plurality of components in this manner, the negative electrode layer can also be referred to as a "negative electrode composite material layer."

The content of the negative electrode active material in the negative electrode layer is usually 50% by weight or more and 95% by weight or less based on the total amount of the negative electrode layer, and is preferably from the viewpoint of further improving the initial charge/discharge efficiency and cycle characteristics of the negative electrode active material. The content is 70% by weight or more and 95% by weight or less, more preferably 85% by weight or more and 95% by weight or less.

The negative electrode layer may include a conventional negative electrode active material in addition to the coated negative electrode active material described above. When the negative electrode layer includes a conventional negative electrode active material as well as the above-described coated negative electrode active material, the content of the negative electrode active material described above is the content of the entire negative electrode active material. Conventional negative electrode active materials are, for example, materials that contribute to intercalation and desorption of lithium ions. From this point of view, conventional negative electrode active materials are not particularly limited, and include, for example, silicon-based materials, carbon-based materials, or mixtures thereof that can constitute the negative electrode active material core material of coated negative electrode active materials. It will be done. The above-mentioned coated type negative electrode layer is used from the viewpoint that the secondary battery obtains a higher theoretical capacity (in other words, battery capacity), and the negative electrode layer is less likely to expand and contract during charging and discharging, and the electrolyte is less likely to decompose. It is preferable to include a carbon-based material (particularly graphite, preferably artificial graphite) as a conventional negative electrode active material together with the negative electrode active material. The mixing ratio of the coated negative electrode active material and the conventional negative electrode active material (especially carbon-based materials) is usually 1/99 or more and 99/1 or less, and the theoretical capacity (in other words, battery capacity) of the secondary battery, charging and discharging From the viewpoint of further improving the expansion/shrinkage resistance of the negative electrode layer and the decomposition resistance of the electrolytic solution, the ratio is preferably 10/90 or more and 50/50 or less, more preferably 20/80 or more and 40/60 or less.

The binder contained in the negative electrode layer is not particularly limited, but may include styrene-butadiene rubber, polyacrylic acid and its salts, polyurethane, polyvinylidene fluoride, polyimide resin, polyaramid resin, and polyamideimide resin. At least one selected from the group consisting of: In a more preferred embodiment, the binder contained in the negative electrode layer is polyvinylidene fluoride. The conductive additive that can be contained in the negative electrode layer is not particularly limited, but includes carbon black (including scaly carbon) such as thermal black, furnace black, channel black, Ketjen black and acetylene black, graphite, Examples include at least one selected from carbon fibers such as carbon nanotubes and vapor grown carbon fibers, metal powders such as copper, nickel, aluminum and silver, and polyphenylene derivatives. Note that the negative electrode layer may contain a thickener component (for example, methyl cellulose) used during battery manufacture.

The thickness of the negative electrode layer after drying, pressing, and vacuum drying is not particularly limited, and may be, for example, 1 μm or more and 300 μm or less, particularly 5 μm or more and 100 μm or less. The thickness of the negative electrode layer is the thickness inside the secondary battery, and the average value of measurements at 50 arbitrary locations is used.

The negative electrode current collector is a member that helps collect and supply electrons generated in the active material due to battery reactions. Such a current collector may be a sheet-like metal member and may have a porous or perforated form. For example, the current collector may be metal foil, punched metal, mesh, expanded metal, or the like. The negative electrode current collector used in the negative electrode is preferably made of a metal foil containing at least one selected from the group consisting of copper, stainless steel, nickel, etc., and may be, for example, a copper foil.

In the negative electrode, a negative electrode layer may be provided on at least one side of the negative electrode current collector. For example, in the negative electrode, negative electrode layers may be provided on both sides of a negative electrode current collector, or a negative electrode layer may be provided on one side of the negative electrode current collector. From the viewpoint of further increasing the capacity of batteries (particularly secondary batteries), a preferred negative electrode has negative electrode layers provided on both sides of a negative electrode current collector.

The negative electrode is prepared by, for example, applying a negative electrode layer slurry prepared by mixing a negative electrode active material and a binder in a dispersion medium to a negative electrode current collector, drying it, and then rolling the dried coating film with a roll press machine or the like. Obtainable.

Preferred embodiments of the negative electrode manufacturing method are as follows.
A coated negative electrode active material (and, if desired, a conventional negative electrode active material), a binder, a dispersion medium (particularly a nonaqueous solvent), and the like are mixed. After this, the mixture may be stirred. Although the stirring method and stirring conditions are not particularly limited, for example, a stirring device such as a mixer may be used. The type of non-aqueous solvent is one that is capable of dispersing the coated negative electrode active material (and the conventional negative electrode active material mixed if desired) and is capable of dissolving the binder. There is no particular limitation as long as there is one or two or more types. This non-aqueous solvent is, for example, an organic solvent such as N-methyl-2-pyrrolidone. Since the binder is dissolved in such a non-aqueous solvent, a non-aqueous dispersion containing the coated negative electrode active material (and optionally mixed conventional negative electrode active material) and the binder is prepared. The state of this non-aqueous dispersion is not particularly limited, but is, for example, paste-like. The paste-like non-aqueous dispersion is a so-called slurry.

Next, a negative electrode is manufactured using the non-aqueous dispersion. In this case, for example, a non-aqueous dispersion is applied to both sides of the negative electrode current collector, and then the non-aqueous dispersion is dried. As a result, a negative electrode layer containing a coated negative electrode active material (and a conventional negative electrode active material if desired) and a binder is formed, so that a negative electrode is completed. Thereafter, the negative electrode layer may be compression molded using a roll press machine or the like. In this case, the negative electrode layer may be heated or compression molding may be repeated multiple times. Compression conditions and heating conditions are not particularly limited.

[battery]
The present invention provides batteries such as secondary batteries and primary batteries. In this specification, the term "secondary battery" refers to a battery that can be repeatedly charged and discharged. The term "secondary battery" is not excessively limited by its name, and may also include, for example, a "power storage device". The term "primary battery" refers to a battery that can only be discharged. The battery of the present invention is preferably a secondary battery.

The secondary battery of the present invention includes the above-described negative electrode. In the secondary battery of the present invention, in addition to the above-mentioned negative electrode, a positive electrode, a separator disposed between the positive electrode and the negative electrode, and an electrolyte are usually enclosed in an exterior body.

In the secondary battery of the present invention, the positive electrode, the negative electrode, and the separator disposed between the positive electrode and the negative electrode constitute an electrode assembly. In the secondary battery of the present invention, the electrode assembly may have any structure as long as the above-described negative electrode (particularly the above-described coated negative electrode active material) is included. This is because, no matter what structure the electrode assembly has, the effect of improving the initial charge/discharge efficiency and cycle characteristics of the negative electrode active material can be obtained. Structures that the electrode assembly may have include, for example, a laminated structure (planar layered structure), a wound structure (jellyroll structure), or a stack-and-fold structure. Specifically, for example, the electrode assembly may have a planar layered structure in which one or more positive electrodes and one or more negative electrodes are laminated in a planar manner with a separator in between. For example, the electrode assembly may have a wound structure (jelly roll type) in which a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode are wound into a roll. For example, the electrode assembly may have a so-called stack-and-fold structure in which a positive electrode, a separator, and a negative electrode are stacked on a long film and then folded.

The positive electrode is composed of at least a positive electrode layer and a positive electrode current collector (foil), and the positive electrode layer may be provided on at least one side of the positive electrode current collector. For example, in the positive electrode, a positive electrode layer may be provided on both sides of a positive electrode current collector, or a positive electrode layer may be provided on one side of the positive electrode current collector. From the viewpoint of further increasing the capacity of the secondary battery, a preferred positive electrode has positive electrode layers provided on both sides of a positive electrode current collector.

The positive electrode layer contains a positive electrode active material. The above-mentioned negative electrode active material contained in the negative electrode layer and positive electrode active material contained in the positive electrode layer are substances directly involved in the transfer of electrons in secondary batteries, and are the main materials of the positive and negative electrodes responsible for charging and discharging, that is, battery reactions. be. More specifically, ions are brought to the electrolyte due to the "positive electrode active material contained in the positive electrode layer" and the "negative electrode active material contained in the negative electrode layer," and these ions move between the positive electrode and the negative electrode. As a result, electrons are transferred and charged and discharged. The positive electrode and the negative electrode are preferably electrodes capable of intercalating and deintercalating lithium ions, that is, the positive electrode layer and the negative electrode layer are preferably layers capable of intercalating and deintercalating lithium ions. In other words, a secondary battery in which lithium ions move between a positive electrode and a negative electrode via an electrolyte to charge and discharge the battery is preferable. When lithium ions are involved in charging and discharging, the secondary battery according to this embodiment corresponds to a so-called "lithium ion battery."

The positive electrode active material of the positive electrode layer is composed of, for example, granules, and preferably contains a binder to ensure sufficient contact between the particles and maintain their shape, and a conductive aid to facilitate the transmission of electrons that promote battery reactions. The agent may be included in the positive electrode layer. Since the positive electrode layer contains a plurality of components in this manner, the positive electrode layer can also be referred to as a "positive electrode composite layer."

The positive electrode active material is preferably a material that contributes to intercalation and desorption of lithium ions. From this point of view, it is preferable that the positive electrode active material is, for example, a lithium-containing composite oxide. More specifically, the positive electrode active material is preferably a lithium transition metal composite oxide containing lithium and at least one transition metal selected from the group consisting of cobalt, nickel, manganese, and iron. That is, in the positive electrode layer of the secondary battery according to this embodiment, such a lithium transition metal composite oxide is preferably contained as a positive electrode active material. For example, the positive electrode active material may be lithium cobalt oxide, lithium nickel oxide, lithium manganate, lithium iron phosphate, or a material in which some of the transition metals thereof are replaced with another metal. Although such positive electrode active materials may be contained as a single species, they may be contained in a combination of two or more types. In a more preferred embodiment, the positive electrode active material contained in the positive electrode layer is lithium cobalt oxide.

The binder contained in the positive electrode layer is not particularly limited, but includes polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, polytetrafluoroethylene, etc. At least one selected from the group consisting of: In a more preferred embodiment, the binder of the positive electrode layer is polyvinylidene fluoride.

The binder content in the positive electrode layer is usually 0.1% by weight or more and 20% by weight or less based on the total amount of the positive electrode layer, and is preferably from the viewpoint of further improving the initial charge/discharge efficiency and cycle characteristics of the negative electrode active material. The content is 0.1% by weight or more and 10% by weight or less, more preferably 0.5% by weight or more and 8% by weight or less.

The conductive additives that can be included in the positive electrode layer include, but are not particularly limited to, carbon blacks such as thermal black, furnace black, channel black, Ketjen black, and acetylene black, graphite, carbon nanotubes, and vapor-grown carbon. Examples include at least one selected from carbon fibers such as fibers, metal powders such as copper, nickel, aluminum, and silver, and polyphenylene derivatives. In a more preferred embodiment, the conductive additive of the positive electrode layer is carbon black (particularly Ketjen black).

In a further preferred embodiment, the binder and conductive additive of the positive electrode layer are a combination of polyvinylidene fluoride and carbon black (particularly Ketjen black).

The content of the conductive additive in the positive electrode layer is usually 0.1% by weight or more and 20% by weight or less based on the total amount of the positive electrode layer, and from the viewpoint of further improving the initial charge/discharge efficiency and cycle characteristics of the negative electrode active material, The content is preferably 0.1% by weight or more and 10% by weight or less, more preferably 0.5% by weight or more and 8% by weight or less.

The thickness of the positive electrode layer (after drying) is not particularly limited, and may be, for example, 1 μm or more and 300 μm or less, particularly 5 μm or more and 200 μm or less. The thickness of the positive electrode layer is the thickness inside the battery (particularly the secondary battery), and the average value of measurements at 50 arbitrary locations is used.

The positive electrode current collector is a member that helps collect and supply electrons generated in the active material due to battery reactions. Such a current collector may be a sheet-like metal member and may have a porous or perforated form. For example, the current collector may be metal foil, punched metal, mesh, expanded metal, or the like. The positive electrode current collector used in the positive electrode is preferably made of a metal foil containing at least one selected from the group consisting of aluminum, stainless steel, nickel, etc., and may be, for example, an aluminum foil.

The positive electrode is prepared by, for example, applying a positive electrode layer slurry prepared by mixing a positive electrode active material and a binder in a dispersion medium to a positive electrode current collector, drying it, and then rolling the dried coating film with a roll press machine or the like. Obtainable.

The separator is a member provided from the viewpoint of preventing short circuits due to contact between positive and negative electrodes and retaining electrolyte. In other words, the separator can be said to be a member that allows ions to pass through while preventing electronic contact between the positive electrode and the negative electrode. Preferably, the separator is a porous or microporous insulating member, which has a membrane form due to its small thickness. By way of example only, a microporous membrane made of polyolefin may be used as the separator. In this regard, the microporous membrane used as the separator may contain, for example, only polyethylene (PE) or polypropylene (PP) as the polyolefin. Furthermore, the separator may be a laminate composed of a "microporous membrane made of PE" and a "microporous membrane made of PP." The surface of the separator may be covered with an inorganic particle coating layer and/or an adhesive layer. The surface of the separator may have adhesive properties.

The thickness of the separator is not particularly limited, and may be, for example, 1 μm or more and 100 μm or less, particularly 5 μm or more and 30 μm or less. The thickness of the separator is the thickness inside the secondary battery (particularly the thickness between the positive electrode and the negative electrode), and the average value of the measured values at 50 arbitrary locations is used.

The electrolyte assists in the movement of metal ions released from the electrodes (positive and negative electrodes). The electrolyte may be a "non-aqueous" electrolyte such as an organic electrolyte and an organic solvent, or an "aqueous" electrolyte containing water. The secondary battery of the present invention is preferably a non-aqueous electrolyte secondary battery in which an electrolyte containing a "non-aqueous" solvent and a solute is used as the electrolyte. The electrolyte may have a liquid or gel form (in this specification, a "liquid" non-aqueous electrolyte is also referred to as a "non-aqueous electrolyte solution").

As a specific non-aqueous electrolyte solvent, one containing at least carbonate is preferable. Such carbonates may be cyclic carbonates and/or linear carbonates. Although not particularly limited, examples of the cyclic carbonates include at least one selected from the group consisting of propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC), and vinylene carbonate (VC). be able to. Examples of chain carbonates include at least one selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), ethylmethyl carbonate (EMC), and dipropyl carbonate (DPC). In one preferred embodiment of the invention, a combination of cyclic carbonates and linear carbonates is used as the non-aqueous electrolyte, for example a mixture of ethylene carbonate and ethyl methyl carbonate.
As a specific solute of the non-aqueous electrolyte, for example, Li salts such as LiPF ₆ and LiBF ₄ are preferably used.

The exterior body is not particularly limited, and may be, for example, a flexible pouch (soft bag) or a hard case (hard housing).

When the outer package is a flexible pouch, the flexible pouch is usually formed from a laminate film, and sealing is achieved by heat sealing the periphery. As a laminate film, a film in which a metal foil and a polymer film are laminated is generally used, and specifically, a three-layer structure consisting of an outer layer polymer film/metal foil/inner layer polymer film is exemplified. The outer polymer film is for preventing damage to the metal foil due to permeation of moisture and contact, and polymers such as polyamide and polyester can be suitably used. The metal foil is for preventing the permeation of moisture and gas, and foils of copper, aluminum, stainless steel, etc. can be suitably used. The inner layer polymer film is used to protect the metal foil from the electrolyte contained therein and to melt and seal it during heat sealing, and polyolefin (for example, polypropylene) or acid-modified polyolefin can be suitably used. The thickness of the laminate film is not particularly limited, and is preferably, for example, 1 μm or more and 1 mm or less.

When the exterior body is a hard case, the hard case is usually formed from a metal plate, and sealing is achieved by irradiating the peripheral edge with a laser. The metal plate is generally made of a metal material such as aluminum, nickel, iron, copper, or stainless steel. The thickness of the metal plate is not particularly limited, and is preferably, for example, 1 μm or more and 1 mm or less.

<Negative electrode active material core material>
A Si-based material (ie, silicon oxide) was prepared as a negative electrode active material core material.
Specifically, SiO (median diameter 7 μm) and SiTi _0.3 (median diameter 3 μm) were used.

<First metal alkoxide>
The following compound was prepared as the first metal alkoxide.
・Tetraethoxysilane (corresponding to the above compound (1A-1))
・Tetrabutoxytitanium (corresponding to the above compound (1B-1))
・Triisopropoxyaluminum (corresponding to the above compound (1C-1))

<Second metal alkoxide>
The following compound was prepared as a second metal alkoxide.
・The above compound (2A-1)
・The above compound (2A-2)
・The above compound (2D-1)
・The above compound (2E-1)
・The above compound (2F-1)

<Example 1>
(Manufacture of negative electrode active material)
70 g of ethanol in which 10.0 g of 28% by weight aqueous ammonia was dissolved was prepared. 60 g of SiO was added to this solution. Next, the first metal alkoxide and the second metal alkoxide were added so that the amounts used were as shown in Table 3 based on 100 parts by weight of SiO added. Thereafter, the mixture was stirred at room temperature (20° C.) for 120 minutes. The reaction solution was filtered and washed with acetone, and the coated powder was dried at 80° C. for 120 minutes to form a film (thickness: 3 nm) on the surface of SiO. This completed the production of SiO (negative electrode active material) coated with the organic-inorganic hybrid film.

(Manufacturing of batteries)
・Negative electrode production process The negative electrode was produced as follows. First, 28.79% by weight of the above negative electrode active material, 67.16% by weight of carbon-based active material (artificial graphite, median diameter D50 = 13 μm), 3.00% by weight of polyvinylidene fluoride, and 1.00% by weight of acetylene black. After mixing 0.05% by weight of carbon nanotubes and a solvent (that is, pure water), the mixture was kneaded and stirred using a rotation-revolution mixer to obtain a negative electrode layer slurry. This negative electrode layer slurry was applied to one side of a 12 μm copper foil, dried at 120°C, pressured with a hand press until it reached 1.7 g/cc, and vacuum dried to form a silicon/graphite mixed negative electrode. was created. The thickness of the negative electrode layer was 36 μm.

-Production process of positive electrode The positive electrode was produced as follows. First, 98 parts by mass of a positive electrode active material (LiCoO2), 1 part by mass of a positive electrode binder (polyvinylidene fluoride), 1 part by mass of a positive electrode conductive agent (Ketjenblack), and an organic solvent (N-methyl-2-pyrrolidone). After mixing, the mixture was stirred (kneaded) using a rotation-revolution mixer to obtain a paste-like positive electrode layer slurry. Next, a positive electrode layer slurry was applied to one side of a positive electrode current collector (aluminum foil with a thickness of 15 μm) using a coating device, and then the positive electrode layer slurry was dried (drying temperature = 120°C) to form a positive electrode layer. Formed. Finally, the positive electrode layer was compression-molded using a hand press machine, and then the positive electrode layer was vacuum-dried. In this case, the volume density of the positive electrode layer was 3.7 g/cc (=3.7 g/cm ³ ).

- Coin cell production process A 25 μm thick microporous polyethylene film was used as the separator. Using an electrolytic solution in which LiPF6 was dissolved at a concentration of 1 mol/kg in a solvent with a weight ratio of ethylene carbonate (EC)/dimethyl carbonate (DMC)/fluoroethylene carbonate (FEC) = 32/65/3, 2016 size A coin cell was created.

(Evaluation of battery characteristics)
- Discharge capacity maintenance rate Using a coin cell, 100 cycles of charging and discharging were performed under the following conditions.
^1st cycle charging: CCCV charging 0.2C-4.4V, 0.025Ccut
^1st cycle discharge: CC discharge 0.2C-2.5Vcut
Charging after ^2nd cycle: CCCV charging 0.5C-4.4V, 0.025Ccut
Discharge after ^2nd cycle: CC discharge 0.5C-2.5Vcut

Specifically, first, in order to stabilize the battery state, the secondary battery was charged and discharged for one cycle in a normal temperature environment (23° C.). During the first cycle of charging, the battery was charged with a current of 0.2C until the voltage reached 4.4V, and then further charged with a voltage of 4.4V until the current reached 0.025C. During the first cycle of discharge, the battery was discharged with a current of 0.2C until the voltage reached 2.5V. Subsequently, the discharge capacity was measured by repeatedly charging and discharging the secondary battery in the same environment until the total number of cycles reached 100 cycles. During the second and subsequent charging cycles, the battery was charged with a current of 0.5C until the voltage reached 4.4V, and then further charged with a voltage of 4.4V until the current reached 0.025C. During the second cycle and subsequent discharges, the battery was discharged with a current of 0.5C until the voltage reached 2.5V. Note that "0.2C" is a current value that completely discharges the battery capacity (theoretical capacity) in 5 hours. "0.025C" is a current value that completely discharges the battery capacity in 40 hours. "0.5C" is a current value that completely discharges the battery capacity in 2 hours. Finally, the discharge capacity during the second cycle of discharge and the discharge capacity during the 100th cycle of discharge were substituted into the following formula to determine and evaluate the discharge capacity retention rate.

◎◎; 93% or more (best);
◎; 90% or more and less than 93% (excellent);
○: 85% or more and less than 90% (good);
×: Less than 85% (problems).

・Discharge load maintenance rate A coin cell was used to charge and discharge under the following conditions.
^1st cycle charging: CCCV charging 0.2C-4.4V, 0.025Ccut
^1st cycle discharge: CC discharge 0.2C-2.5Vcut
^2nd cycle charging: CCCV charging 0.2C-4.4V, 0.025Ccut
^2nd cycle discharge: CC discharge 0.2C-2.5Vcut
^3rd cycle charging: CCCV charging 0.2C-4.4V, 0.025Ccut
^3rd cycle discharge: CC discharge 0.5C-2.5Vcut
^4th cycle charging: CCCV charging 0.2C-4.4V, 0.025Ccut
^4th cycle discharge: CC discharge 2.0C-2.5Vcut

In detail, using a secondary battery (charged and discharged for 1 cycle) whose battery condition has been stabilized using the same procedure as when examining the discharge capacity retention rate (cycle characteristics), discharge in a room temperature environment (23°C). The secondary battery was further charged and discharged for 3 cycles while changing the current, and the discharge capacity was measured in the 2nd cycle and the 4th cycle. During the second to fourth charging cycles, the battery was charged with a current of 0.2C until the voltage reached 4.4V, and then further charged with a voltage of 4.4V until the current reached 0.025C. During the second cycle of discharge, the battery was discharged at a current of 0.2C until the voltage reached 2.5V. During the third cycle of discharge, the battery was discharged with a current of 0.5C until the voltage reached 2.5V. During the fourth cycle of discharge, the battery was discharged with a current of 2C until the voltage reached 2.5V. From this measurement result, the discharge load maintenance rate was determined and evaluated based on the following formula. Note that "2C" is a current value that completely discharges the battery capacity in 0.5 hours.

◎◎; 90% or more (best);
◎; 85% or more and less than 90% (excellent);
○: 80% or more and less than 85% (good);
×: Less than 80% (problems).

<Examples 2 to 20 and Comparative Examples 1 to 3>
When producing the negative electrode active material, battery production and battery characteristics were carried out in the same manner as in Example 1, except that the types and blending amounts of the first metal alkoxide and second metal alkoxide were changed as shown in Table 3. We conducted an evaluation.

The secondary battery according to the present invention can be used in various fields where power storage is expected. Although this is merely an example, the secondary battery according to the present invention, particularly the nonaqueous electrolyte secondary battery, can be used in the electrical, information, and communication fields where mobile devices are used (e.g., mobile phones, smartphones, smart watches, laptop computers, etc.). , digital cameras, activity monitors, arm computers, electronic paper, and other mobile devices), household and small industrial applications (e.g., power tools, golf carts, household, nursing care, and industrial robots), and large industrial applications. (e.g., forklifts, elevators, harbor cranes), transportation systems (e.g., hybrid vehicles, electric vehicles, buses, trains, electrically assisted bicycles, electric motorcycles, etc.), power system applications (e.g., various power generation, Fields such as road conditioners, smart grids, and general home-installed energy storage systems), medical applications (medical devices such as earphones and hearing aids), pharmaceutical applications (fields such as medication management systems), IoT fields, and space/deep sea applications. (For example, in the field of space probes, underwater research vessels, etc.).

1: Negative electrode active material core material 2: Organic-inorganic hybrid coating 10: Negative electrode active material

Claims (8)

Negative electrode active material core material; and
having a coating formed on the surface of the negative electrode active material core material,
The coating is
a first metal alkoxide containing no metal atom-carbon atom bond in one molecule; and
Second metal alkoxide containing two or more metal atom-carbon atom bonds in one molecule
A method for producing a negative electrode active material for a battery, which is an organic-inorganic hybrid coating consisting of a reactant containing at least
Stirring the negative electrode active material core together with the first metal alkoxide and the second metal alkoxide in an alkaline solvent,
The first metal alkoxide is a compound represented by the following general formula (1),

(In formula (1), M ¹ is Si, Ti, Al or Zr;
x is the valence of M ¹ and is an integer of 3 or 4;
R ¹ is each independently an alkyl group having 1 to 10 carbon atoms or -C(R ² )=CH-CO-R ³ (wherein R ² is an alkyl group having 1 to 10 carbon atoms; , R ³ is an alkyl group having 1 to 30 carbon atoms, an alkyloxy group having 1 to 30 carbon atoms, or an alkenyloxy group having 1 to 30 carbon ^atoms ; When R ¹ is the alkyl group, it may be bonded to each other to form one ring together with the oxygen atom to which the two R ^1s are bonded and the M ¹ atom to which the oxygen atom is bonded . )
The second metal alkoxide is a compound having two or more Si atom-carbon atom bonds in one molecule, and has the following general formulas (2A), (2B), (2C), (2D), ( 2E) or (2F), or a mixture thereof;

(In formula (2A), R ²¹¹ and R ²¹² are each independently an alkyl group having 1 to 10 carbon atoms;
R ³¹ is a divalent hydrocarbon group having 1 to 20 carbon atoms)

(In formula (2B), R ²¹¹ , R ²¹² , R ²¹³ and R ²¹⁴ are each independently an alkyl group having 1 to 10 carbon atoms;
R ³² are each independently a divalent hydrocarbon group having 1 to 20 carbon atoms;
R ³³ are each independently a monovalent hydrocarbon group having 1 to 10 carbon atoms)

(In formula (2C), R ²¹¹ and R ²¹² are each independently an alkyl group having 1 to 10 carbon atoms;
R ³⁴ , R ³⁵ , and R ³⁶ are each independently a divalent hydrocarbon group having 1 to 10 carbon atoms)

(In formula (2D), R ²¹¹ and R ²¹² are each independently an alkyl group having 1 to 10 carbon atoms)

(In formula (2E), R ²¹² and R ²¹³ are each independently an alkyl group having 1 to 10 carbon atoms;
R ³² are each independently a divalent hydrocarbon group having 1 to 20 carbon atoms;
R ³³ are each independently a monovalent hydrocarbon group having 1 to 10 carbon atoms;
R ³⁴ are each independently a monovalent hydrocarbon group having 1 to 30 carbon atoms)

(In formula (2F), R ²¹² , R ²¹³ and R ²¹⁴ are each independently an alkyl group having 1 to 10 carbon atoms;
each R ³² is independently a divalent hydrocarbon group having 1 to 20 carbon atoms)
The method for producing a negative electrode active material, wherein the content of the coating is 0.30% by weight or more and 1.00% by weight or less based on the total amount of the negative electrode active material. The negative electrode active according to claim 1, wherein the coating contains 10% by weight or more and 95% by weight or less of the first metal alkoxide and 5% by weight or more and 90% by weight or less of the second metal alkoxide, based on the total amount thereof . A method of manufacturing a substance. The method for producing a negative electrode active material according to claim 1 or 2 , wherein the negative electrode active material core material contains at least Si. The method for producing a negative electrode active material according to any one of claims 1 to 3 , wherein the battery is a lithium ion secondary battery. A method for manufacturing a negative electrode comprising a negative electrode layer and a negative electrode current collector , comprising the method for manufacturing a negative electrode active material according to any one of claims 1 to 4 . A method for manufacturing a secondary battery, comprising a negative electrode , a positive electrode, a separator disposed between the positive electrode and the negative electrode, and an electrolyte, the method comprising the method for manufacturing a negative electrode according to claim 5 . The method for manufacturing a secondary battery according to claim 6 , wherein the electrolyte is a nonaqueous electrolyte. 8. The method for manufacturing a secondary battery according to claim 6 , wherein the positive electrode and the negative electrode are electrodes capable of inserting and extracting lithium ions.

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